To answer this you will need to know that there are 43,560 square feet in 1 acre.
1. Half of this is 43560/2 or 21780 square feet.
2. Out of this amount Blake has already mowed 3/5 of the lawn. This means he must mow 2/5 (1 - 3/5) more.
2/5 of 21,780 ft.² can be represented this way:
2/5 x 21780 =?
He needs to mow 8712 ft.² more.
